Elementary circular slide rule

ABSTRACT

This invention relates to a circular slide rule which is particularly adapted for facilitating the learning process of addition and/or subtraction by primary grade students. The slide rule includes a bottom disc, a top disc, and a problem indicator, all coaxially mounted for relative rotation. The problem indicator, in a preferred embodiment, defines a window which is adapted to display only a single number from a scale on the bottom disc and a single number from the scale on the top disc. The algebraic sum of the two numbers displayed in the window of the indicator is read off on one of the scales as being the number opposite to an answer mark on the other scale.

United States Patent [191 Long [ 1 3,747,846 1 July 24, 1973 ELEMENTARYCIRCULAR SLIDE RULE [76] Inventor: William C. Long, 6415 Indigo,

Houston, Tex. 77036 [22] Filed: July 8, 1971 [21] Appl. No.: 160,642

Primary Examiner-Stephen J. Tomsky Attorney-Michael P. Breston [57]ABSTRACT This invention relates to a circular slide rule which isparticularly adapted for facilitating the learning process of additionand/or subtraction by primary grade students. The slide rule includes abottom disc, a top disc, and a problem indicator, all coaxially mountedfor relative rotation. The problem indicator, in a preferred embodiment,defines a window which is adapted to display only a single number from ascale on the bottom disc and a single number from the scale on the topdisc. The algebraic sum of the two numbers displayed in the window ofthe indicator is read off on one of the scales as being the numberopposite to an answer mark on the other scale.

3 Claims, 6 Drawing Figures mmm JUL 2419?; 346

sum 1 or 2 INVENTOR. WILLIAM C. LQNG,

MICHAEL P. BRESTON ATTORNEY.

PATENIED JUL 2 4 I813 snail 2 [IF 2 FIC5.5.. F|G.6

h 80 INVENTOR.

J WILLIAM 0. LONG,

MICHAEL P. BRESTON ATTORNEK ELEMENTARY CIRCULAR SLIDE RULE BACKGROUND OFTHE INVENTION Various educational devices have been proposed forfacilitating a childs process of learning elementary additions andsubtractions. A most common method, even at present, is for the child touse its fingers to obtain the answers to simple arithmetic problemsinvolving additions and subtractions. While being very dependable, thismethod is time consuming and limited by the number of available fingers.

Flash cards are also frequently employed as an aid in teachingelementary arithmetic problems. Such cards, while serving a usefulporpose, have certain wellknown drawbacks: the cards have to be keptsorted, each problem is usually set out on a separate card, and childrenfrequently lose some of the cards. In addition, by providing the problemand the answer on the same card, the challenge which is normallyassociated with setting up the problem and with independently findingits solution is not available to the child when using such flash cards.

Various mechanical educational devices, including slide rules, have beenproposed. Such devices and slide rules as are known to me have definitelimitations which can be summarized as follows: most of such devices setup the arithmetic problem through methods which are too cumbersomefor aprimary grade student. The straight slide rules, in which a problem canbe set up at one position and the answer read at another position, arelimited to one mode of operation only, that is either to addition or tosubtraction. Also, the sliding member in such straight slide rulesfrequently becomes lost.

Accordingly, it is a main object of this invention to provide a new andimproved circular slide rule. The disposition of the scales on the sliderule's rotatable discs is such that their inter-relationship can beeasily comprehended by a beginner in arithmetic.

It is another object of this invention to provide such a circular sliderule which allows speed of operation, and which can be inexpensivelymanufactured.

It is a further object of this invention to provide such a circularslide rule which greatly facilitates the learning process of simpleadditions and subtractions by primary grade students.

SUMMARY OF THE INVENTION A The circular slide rule of this inventionincludes at least two discs and one problem indicator all stacked incoaxial relationship for relative movement therebetween. The bottom dischas a relatively large diameter and bears near its outer periphery oneach face thereof a circular numerical scale which is divided into equalarcuate increments. The top disc bears near its outer periphery on eachface thereof a similar numerical scale. The arcuate increments on bothscales are subtended by the same angular value.

The problem indicator defines, in a preferred embodiment, a windowoverlapping both scales and extending in a radial direction fordisplaying only one number from eachscale. The numbers appearing in thewindow are to be added or subtracted. The answer to the problem is readon one scale opposite to an answer marker on the other scale. Problemsof addition are solved by using scales on one side of the discs, and

problems of subtraction are solved by using scales on the opposite sideof the discs.

Other embodiments using the same or similar principles can include meansfor electrically controlling the readout of the answer, as byilluminating the answer, or by pointing to the answer with a movablemechanical pointer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic top view of oneside of a preferred embodiment of the circular slide rule of thisinvention;

FIG. 2 is a schematic top view of the opposite side of the embodimentshown in FIG. 1;

FIG. 3 is a front view in elevation of another embodiment of thisinvention;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is a sectional view of yet another circular slide rule embodyinga modification to the embodiment shown in FIG. 4; and

FIG. 6 is a partial view of a modified problem indicator for theembodimentshown in FIGS. 1 and 2.

In the drawings, the same reference characters designate the same orsimilar parts.

Referring now to the embodiment illustrated in FIGS. 1 and 2, thecircular slide rule of this invention is gener ally referenced as 10.Slide rule 10 includes a bottom disc 12, a top disc 14, and a foldedproblem indicator 16, all stacked in a coaxial relationship for relativerotation on a stub shaft 18 to which they can be detach ably secured bya nut (not shown), or by any other means.

The diameter of disc 12 is larger than that of disc 14. Indicator 16preferably-defines in each side thereof a radially-extending, indexpreferably in the form of a slot or window 20. Inscribed near the outeredges of discs 12 and 14 are circular, numerical scales 22 and 24,respectively. Each of scales 22, 24 is divided into arcuate incrementsof equal length which are subtended by the same angular value, as shown.The area of the opening defined by window 20 is such as to allow thedisplay of only one number from each scale.

When the scales have their numbers progressively advancing in the samedirection, say clockwise, as in FIG. 1, the numbers appearing in thewindow of the problem indicator 16 are set up for subtraction. 0n theother hand, if the scales have their numbers progressively advancing inopposite directions, as shown in FIG. 2, the numbers appearing in thewindow of the problem indicator 16 are set up for addition.

In the case of subtraction (FIG. 1), the answer indicator 25 on scale 24(which is also the zero mark) points to the number on scale 22 which isthe answer to the problem. Thus in FIG. 1, 22-l4=8.

In the case of addition (FIG. 2), the answer indicator 26 on scale 22(which is also the zero mark) points to the number on scale 24 which isthe answer to the problem. Thus in FIG. 2, l5+l6=31.

In the case of addition,stop lugs 27, 28 are provided on the face ofdisc 14 to prevent indicator 16 from moving to a number which wouldcause the slide rule 10 to become off scale. Thus in FIG. 2, the highestanswer is the number 31 (15+16). For this reason the scale 22 in FIG. 2extends only from 0 to 15.

Referring now to the embodiment shown in FIGS. 3 and 4, the circularslide rule, now generally designated as 40, includes an inner, annularmember 42 having a C-shaped cross-section and comprising a translucentring 44. On ring 44 is inscribed a circular scale 46 similar to scale22. Scale 46 advances in a clockwise direction. Rotatably mounted withmember 42 is a disc 47 which detachably supports an annular,interchangeable scale 48 similar to scale 24. Scale 48 may have itsnumbers progressing in a counter-clockwise direction or in a clockwisedirection depending, respectively, on whether addition or subtraction isdesired.

In FIGS. 3 and 4, scale 48 advances counterclockwise. A housing 50rotatably supports member 42 and disc 47 on a shaft 52. Ahingedly-mounted, L- shaped problem indicator 54 is provided with aspringbiased, push-button 56 and an index or window 58. Window 58 servesthe same function as index or window 20. A battery 60 mounted on theinside face of disc 47 is electrically connected by wires 62 to asuitable light bulb 64 providing a focused light beam 65. Light bulb 64is mounted on an arm 63 which is mounted to and rotates with disc 47. Aswitch 66, having two terminals 67, 68, is closed by depressingpushbutton 56 which allows a flexible contact spring 70 to electricallycontact both terminals 67 and 68.

In operation of the embodiment shown in FIGS. 3 and 4, to set up theaddition problem, say 4+12 (FIG. 3), the disc 47 is rotated relative toring 44 until the numbers 4 and 12 are opposite each other in window 58.The child is then asked to provide the answer to the problem set up. Thecorrectness of his answer can be checked by depressing push-button 56.The answer to the above given problem is 16, and the number 16 will beilluminated, as shown in FIG. 3, by the light beam 65 on scale 46.

The embodiment illustrated in FIG. is in most respects similar to theembodiment shown in FIG. 4, except that instead of employing a lightsource to illuminate the answer, there is now employed a biasedpointer80 which is normally biased radially inwardly by a coil spring 82. Whenthe answer to the problem is desired, the push-button 56 is pushed in.The piston 84 of button 56 slides inwardly into a bore 86 provided in abushing 88. The conical shoulder 90 of push-button 56 will then causepointer 80 to move downwardly. Pointer 80 will point to the correctanswer on scale 46 in a manner similar to the light beam 65.

In the embodiments shown in FIGS. 4 and 5, the inner scale 48 isdetachably secured to the inner disc 47 in any suitable manner. Scale 48can be turned over to provide on its opposite face a scale with numbersprogressing in an opposite direction, say clockwise for subtraction.Thus, the same scale can be used to perform an algebraic sum which canbe either an addition or a subtraction.

While in the preferred embodiments the problem indicator 16 is shown ashaving a window or index 20, the indicator 17 could instead have aradially-extending index or hairline 92, as shown in FIG. 6.

In FIG. 6, the numbers selected for a subtraction problem are, say, 8and 3 which are aligned under the hairline 92 on scales 22 and 24,respectively.

Among the many advantages derived from using the circular slide rule ofthis invention are the following: the problem is presented with thenumbers aligned vertically, with a or sign, in a manner to which thechild is accustomed; the two scales 22 and 24 can be held together andthe problem indicator 16 rotated to allow the child to learn allcombinations which yield the same answer; or one of the discs 12 or 14,is rotated relative to the other disc and the indicator, bothstationary, to allow the child to learn the answers to progressivelyadvancing problems. Other advantages will readily become apparent fromthe preceding description.

What I claim is:

1. A circular slide rule having a front face for solving elementaryaddition problems by beginners and a back face for solving elementarysubtraction problems, said slide rule comprising:

a first disc having on each face thereof near it outer periphery acircular numerical scale divided into equal-length arcuate segments;

a second disc having on each face thereof near its outer periphery acircular numerical scale divided into equal-length arcuate segments;

said arcuate segments of said first and second discs being subtended bythe same angular value and the diameter of said first disc being largerthan the diameter of said second disc, the scales on the front face ofthe slide rule progressively advancing in opposite circumferentialdirections, and the scales on the back face of the slide ruleprogressively advancing in the same circumferential directions;

a first problem indicator having a radially-extending index;

a second problem indicator having a radiallyextending index;

means rotatably supporting said first and second discs and said firstand second problem indicators for rotation about a common axis extendingthrough the center of each disc, whereby;

the front face of said first disc, the front face of said second disc,and said first problem indicator constitute said front face of saidslide rule, and

the back face of said first disc, the back face of said second disc, andsaid second problem indicator constitute said back face of said sliderule;

a first answer indicator on one of the scales on the front face of saidslide rule;

a second answer indicator on one of the scales on the back face of saidslide rule;

the radially-extending index on the first problem indicator beingadapted to align a single number from the scale on the front face of thefirst disc with a single number on the front face of the second disc,whereby the two aligned numbers constitute a desired problem of additionand the first answer indicator providing the sum of the aligned numbers;

the radially-extending index on the second problem indicate beingadapted to align a single number from the scales on the back face of thefirst disc with a single number on the back face of the second disc,whereby the two aligned numbers constitute a desired problem ofsubtraction and the second answer indicator providing the differencebetween the aligned numbers; and

the body of said first problem indicator defining an opening serving asa window through which only the aligned numbers on the front face of theslide rule are visible.

2. The slide rule of claim 1 wherein the body of said second problemindicator defines an opening serving as a window through which only thealigned numbers on the back face of the slide rule are visible.

3. The slide rule of claim 1 wherein said first and second problemindicators are coupled together at their ends.

t I ll 4 t

1. A circular slide rule having a front face for solving elementaryaddition problems by beginners and a back face for solving elementarysubtraction problems, said slide rule comprising: a first disc having oneach face thereof near it outer periphery a circular numerical scaledivided into equal-length arcuate segments; a second disc having on eachface thereof near its outer periphery a circular numerical scale dividedinto equal-length arcuate segments; said arcuate segments of said firstand second discs being subtended by the same angular value and thediameter of said first disc being larger than the diameter of saidsecond disc, the scales on the front face of the slide ruleprogressively advancing in opposite circumferential directions, and thescales on the back face of the slide rule progressively advancing in thesame circumferential directions; a first problem indicator having aradially-extending index; a second problem indicator having aradially-extending index; means rotatably supporting said first andsecond discs and said first and second problem indicators for rotationabout a common axis extending through the center of each disc, whereby;the front face of said first disc, the front face of said second disc,and said first problem indicator constitute said front face of saidslide rule, and the back face of said first disc, the back face of saidsecond disc, and said second problem indicator constitute said back faceof said slide rule; a first answer indicator on one of the scales on thefront face of said slide rule; a second answer indicator on one of thescales on the back face of said slide rule; the radially-extending indexon the first problem indicator being adapted to align a single numberfrom the scale on the front face of the first disc with a single numberon the front face of the second disc, whereby the two aligned numbersconstitute a desired problem of addition and the first answer indicatorproviding the sum of the aligned numbers; the radially-extending indexon the second problem indicate being adapted to align a single numberfrom the scales on the back face of the first disc with a single numberon the back face of the second disc, whereby the two aligned numbersconstitute a desired problem of subtraction and the second answerindicator providing the difference between the aligned numbers; and thebody of said first problem indicator defining an opening serving as awindow through which only the aligned numbers on the front face of theslide rule are visible.
 2. The slide rule of claim 1 wherein the body ofsaid second problem indicator defines an opening serving as a windowthrough which only the aligned numbers on the back face of the sliderule are visible.
 3. The slide rule of claim 1 wherein said first andsecond problem indicators are coupled together at their ends.